Many studies have reported on the estimation of the development of left ventricular dimensions in children by using two-dimensional echocardiography and formulated equations to evaluate normal cardiac dimensions. We reported that height is the most simple and useful index to evaluate the normal dimensions of the left ventricle in children. Disparities have been detected between the “normal” dimensions estimated from these formulae and real dimensions in infants less than 1 year of age and neonates, by using body weight or body surface area as an index. Our objective is to assess the normal size of left ventricular end-diastolic dimension in infants less than 1 year of age and neonates, including premature neonates, by two-dimensional echocardiography by using height as an index.

The study group consisted of 243 infants, 123 males, and 120 females without congenital cardiac disease. The regression equation for the relationship between left ventricular end-diastolic dimension (Y) and height was Y (millimetre) = 0.352 × height (centimetre) + 1.86 in mature neonates and infants with height of less than 75 centimetres, whereas that in premature neonates was Y (millimetre) = 0.495 × height (centimetre) − 5.43. No significant differences were observed in the infants on the basis of sex.

The regression equations reported in the previous studies cannot be applied to data obtained from infants. In addition, three different formulae, one for each group of infants by using height as an index can be usefully applied for practical purposes.